1. Field of the Disclosure
This disclosure relates generally to trip mechanisms for snowplows and, more specifically, to V-blade snowplows having a dual trip mechanism.
2. Related Technology
Generally speaking, snowplow blades come in two different types, a straight blade and an adjustable or V-blade. The straight blade generally extends across the front of a vehicle, such as a truck. Some straight blades may be angularly adjustable relative to the longitudinal axis of the vehicle. For example, some straight blades may have the capability to angle the straight blade relative to the longitudinal axis of the vehicle. While straight blades generally push snow well, they are not very adaptable to plowing confined areas or odd-shaped areas.
V-blade snowplows, on the other hand, are more adaptable. V-blades are formed by two wings or blades (a driver's side blade or left wing, and a passenger's side blade or right wing) that meet at a center hinge. Each blade may be independently adjustable relative to the longitudinal axis of the vehicle. As a result, the V-blade may have multiple useful configurations. For example, the V-blade may take on a V-shape with each blade extending at an angle from the center hinge, rearwardly toward the vehicle. The V-blade may also take on an inverted V-shape or scoop configuration, where each blade extends at an angle forward from the center hinge, away from the vehicle. Finally, the V-blade may mimic a straight blade by having one blade extend forward from the center hinge and another blade extending rearward from the center hinge. As a result of the different configurations, the V-blade is known to be generally more adaptable to unique plow areas, especially confined plow areas.
In practice, areas to be snow plowed are rarely flat and level. To the contrary, most plowing areas have uneven terrain and even obstacles extending upward from the plowing surface, such as curbs, manhole covers, reflectors, ADA-mandated tactile warning tiles, and other objects. Snowplow blades must have the capability to adjust to the uneven terrain and to overcome the obstacles without breaking the obstacle or the blade. When a snowplow blade meets an obstacle, it “trips” in one or more directions to allow the blade, or a portion of the blade, to adjust so that the snowplow blade may pass over the obstacle. Generally, there are two types of trip mechanisms: An edge trip mechanism and a full blade trip mechanism.
In edge trip mechanisms, a cutting edge strip is hingedly attached along the bottom edge of a main blade or moldboard. The cutting edge strip is biased forward, into general alignment with the bottom of the moldboard, by one or more springs. When an obstacle is encountered, and enough force is generated to overcome the spring bias, the cutting edge strip pivots rearward, allowing the main blade to pass over the obstacle. Once the obstacle has been passed over, the spring-biased cutting edge strip returns, due to the spring bias, to its normal untripped position. The cutting edge strip is typically made of a sacrificial material, such that it is slowly worn away during the plowing process through friction with the plowing surface. As the sacrificial material wears down, the maximum obstacle clearance height is slowly reduced because the maximum height of the cutting edge strip is reduced. Eventually, the user must replace the cutting edges. One drawback of the edge trip mechanisms is that they are obstacle height-limited. In other words, if an obstacle is encountered that is higher than the thin cutting edge strip, the obstacle will contact the main blade (even if the thin cutting edge strip rotates out of the way). Such an encounter can cause damage to the main blade, the blade mounting hardware, and/or the vehicle itself.
In full blade trip mechanisms, the full blade assembly is pivotably mounted to the vehicle. The pivot axis is generally located above the top of the cutting edge. One or more trip springs bias the two moldboards and their respective cutting edges (which, in conventional V-blade plows, were fixedly-, as opposed to hingedly-, secured to the base of the respective moldboards) into a plowing position. When an obstacle is encountered, and the trip spring bias is overcome, the full blade assembly pivots about the pivot axis, which causes the full moldboards to rotate rearward and upward, thereby clearing the obstacle. As with the cutting edges of edge trip mechanisms, once the obstacle has been cleared, the full moldboards return to their original, un-tripped position. While the full blade trip mechanism generally is capable of clearing relatively high obstacles, the force required to overcome the spring bias is greater than edge trip mechanisms, which causes greater impact forces to be transferred to the vehicle. These greater impact forces can be unpleasant for a driver and any other occupants of the vehicle.